1. Field of the Invention
The present invention relates to an ink tank unit for storing the ink to be supplied to a recording head unit for the recording by discharging the ink, an ink jet cartridge having said unit, and an ink jet apparatus which performs the recording with said cartridge mounted thereon.
2. Related Background Art
Recording apparatuses which have the features of a printer, copying machine, facsimile etc., or are useful as the output device for the complex electronic equipment including a computer or a word processor, or the work station, are configured to record the image onto the recording medium such as paper or plastic thin plate, based on image information. Such recording apparatuses can be classified into the ink jet system, the wire dot system, the thermal system and the laser beam system, depending on the recording method.
A recording apparatus of the ink jet system (an ink jet recording apparatus) performs the recording by discharging the ink from recording means (recording head) onto the recording medium, having the following advantages. The recording means can be made compact, a high definition image can be recorded at high speed, the ordinary paper can be used for the recording without any special treatments, the running cost is low, the noise is small owing to the non-impact method, and the color image is easily recorded by using color inks. In particular, a line-type recording apparatus using recording means of the line-type in which a number of discharge ports are arranged in a direction of sheet width allows the higher speed recording.
Specifically, recording means (recording head) of the ink jet system of discharging the ink by the use of heat energy can be easily fabricated with an arrangement of liquid channels (discharge ports) at high density by forming electrothermal converters, electrodes, liquid channel walls, and a celling plate as the film on a substrate through a semiconductor fabrication process such as etching, vapor deposition or sputtering, thereby allowing for the further compact construction.
An ink vessel for use in the ink jet recording apparatus is required to excellently supply the ink corresponding to an ink amount to be discharged from the recording head during the recording, and have no ink leakage through the discharge ports when the recording is not performed.
If the ink vessel is a replaceable type, the ink vessel is required to be easily mounted or demounted, without ink leakage, and surely supply the ink to the recording head.
One of the ink vessels useful for the ink jet recording apparatus is of a constitution as disclosed in Japanese Laid-Open Patent Application No. 63-87242 (hereinafter referred to as a first conventional example), that is, an ink jet recording cartridge having a plurality of ink injection orifices with a foamed member disposed within the ink vessel.
This ink vessel can store the ink in a porous medium such as polyurethane foam which is a foamed member providing negative pressure caused by capillary force of the foam to hold the ink therein (prevent ink leakage from the ink vessel).
Also, Japanese Laid-Open Patent Application No. 2-522 (hereinafter referred to as a second example) discloses an ink jet recording cartridge provided with a porous member between a primary ink reservoir and a secondary ink reservoir and between the secondary ink reservoir and the ink jet recording head.
In this invention, by disposing the porous member only in the ink flow passage but not containing it in the ink reservoir, the ink storable amount is increased as compared with that of the first conventional example. Also, by providing the secondary ink reservoir, the ink distribution or the air flow when the temperature rises or during the recording can be regulated to stabilize the negative pressure of the recording head.
However, since in the first conventional example, the ink storing portion needs the foam substantially over its entire area, the filling amount of the ink is restricted, with more ink unused and left in the foam, resulting in a problem that the ink use efficiency is poor. And there was a further problem that remaining amount of ink is difficult to detect, and the substantially constant negative pressure is difficult to attain during the period of consuming the ink.
Also, as seen in the first conventional example, in an ink cartridge having the form of inserting a foam into the ink storing portion, the corner portion of the foam may be distorted, depending on the way of inserting the foam, when inserting the foam, bringing about uneven compression distribution of the whole foam, with the possibility that the distribution of the ink in the ink storing portion is biased.
In this case, due to a bias of negative pressure generating power, the ink flow passage may be disrupted even if the ink is sufficiently stored, causing a discharge failure, or possibly ink leakage upon impacts as the ink is concentrated near the atmosphere communicating port. Accordingly, when inserting the foam into the ink cartridge, there is requirement for the high precision, with great restrictions on the manufacture.
On the other hand, in the second conventional example, the porous medium as a negative pressure generating member is sufficiently impregnated with the ink because a negative pressure generating member is disposed in the ink flow passage when the recording is not performed, causing insufficient generation of negative pressure with capillary force of the porous medium, resulting in a problem that ink leakage is likely to occur through orifices of the ink jet recording head by slight impact.
Also, in the technical fields of recording using the ink, there is a contact recording technique for use with the plotters. In this contact recording technique, the ink supply is typically made to a recording core or wick having ink absorbability and retainability like a felt-tipped pen.
One example of the ink supply form in the above contact recording technique is Japanese Laid-Open Utility Model Application No. 57-16385. This discloses a recording instrument pen relying on the use of a recording core (porous ink absorptive core) for recording in contact with the recording medium.
The invention which this document discloses adopts a constitution of comprising a central chamber having a recording core, a first flocculent fiber in contact with the recording core, and a second flocculent fiber having small amount of ink absorbed in the upper atmosphere communicating port side and being less permeable to the ink than the first flocculent fiber, and a closed type ink storing chamber from which the ink can be supplied via a communicating hole to either side of the central chamber.
With this constitution, the air within the closed type ink storing chamber expands due to rises in the ambient temperature, so that the ink within the closed type ink storing chamber flows into the first flocculent fiber. The ink exceeding the acceptable impregnated amount of the first flocculent fiber is impregnated by the second flocculent fiber, thereby preventing the ink overflowing from the recording core and dripping down.
Also, there is provided a groove of fixed width to cause the expanded air to escape into the atmosphere communicating port, when one of two closed type ink storing chambers is only filled with the air, the groove extending from the uppermost end to the lowermost end of a lateral surface different from that of a partition wall between the central chamber and the closed type ink storing chamber, as disclosed above.
However, in the above contact recording instrument pen, no attention is paid to the stable generation of negative pressure serving to prevent ink leakage from the recording unit in the ink jet technique which involves a non-contact recording.
Also, the consumption of the ink from the ink storing chambers on both sides is not necessarily identical, but it is pointed out that the ink of one ink storing chamber may be possibly exhausted ahead. Some attention is paid concerning the ink leakage from the recording core due to environmental changes in this case, but in the ink jet recording field, some problem such as the disruption of ink flow passage, or the penetration of air bubbles into the recording portion may occur.
To solve the above background problems, the present inventors have previously made applications for, as the ink vessel suitable for the ink jet print technical field, an ink jet cartridge having both features of the capability of supplying excellently the ink in the amount corresponding to that discharged from the recording head during printing, and the expedience of having no ink leakage from the discharge ports when the printing is not performed (Japanese Laid-Open Patent Application No. 4-198474, Japanese Laid-Open Patent Application No. 4-198681).
Herein, it has been found that the fundamental constitution effective for the ink jet characteristics is one having a first accommodating chamber which is a negative pressure generating member receiving portion having an atmosphere communicating portion for communicating to the atmosphere as well as receiving a negative pressure generating member, and a second accommodating chamber which communicates to the first accommodating chamber but lies in substantially closed state, and which is an ink storing portion for directly storing the ink to be supplied to the first accommodating chamber (hereinafter referred to as a presupposed constitution).
Because this constitution has a tank structure in which the negative pressure can be made substantially constant for most of the term from the initiation of using the head cartridge to the termination thereof, it is possible to provide a replacement-type head cartridge and an ink jet head and a printer which can cope with the high speed recording.
Further, in recent years, the ink jet recording art is not only applied to the printer, but also employed in the communication technical field such as facsimile, the copying machine field usable for the large paper (large size), and in the printing field onto cloth. With this trend, the larger capacity of the ink vessel is desired for the apparatus.